Vehicle lamps including vertically arranged lenses have been proposed (see, for example, Japanese Patent No. 4666160 or U.S. Pat. No. 7,325,954 corresponding to JP Patent No. 4666160).
As shown in FIG. 1, a vehicle lamp 200 described in Japanese Patent No. 4666160 can include vertically arranged lenses 210A and 210B, an HID bulb 220, an upper reflector 230A, a lower reflector 230B, and the like. In the vehicle lamp 200 configured as described above, upward light emitted from the HID bulb 220 can be reflected by the upper reflector 230A, pass through the upper lens 210A, and then be projected toward the front. Downward light emitted from the HID bulb 220 can be reflected by the lower reflector 230B and the like, pass through the lower lens 210B, and then be projected toward the front.
In recent years, semiconductor light-emitting devices such as LEDs are receiving attention from the viewpoint of power saving and the like. In the field of vehicle lamps, it is also contemplated to use semiconductor light-emitting devices instead of HID bulbs and the like.
In general, a semiconductor light-emitting device such as an LED is said to be a light source having directional characteristics. More specifically, the luminous intensity of the light source is maximum on its optical axis and decreases as the inclination with respect to the optical axis increases (see FIG. 6). Therefore, when the HID bulb 220 is simply replaced with a semiconductor light-emitting device such as an LED, the difference between the luminous intensity (difference in luminance) through the upper lens and that through the lower lens is noticeable when the lenses are viewed from a viewpoint in front of the vehicle (a viewpoint above a horizontal line, for example, the viewpoint of a pedestrian in front of the vehicle or the driver of an oncoming vehicle). This causes a problem in that the brightnesses observed through the lenses are different from each other.